Table 5.
Random parameters logit regression results: condition subgroups (N=323)
| Attribute | Preference weight | 95% confidence interval | ||
|---|---|---|---|---|
| axSpA Subgroup | ||||
| Skin sensor | 0.988** | 0.678 | 1.297 | |
| Control of the speed of injection | 0.659** | 0.428 | 0.891 | |
| Step-by-step, on-screen instructions in real time | 0.235* | 0.011 | 0.459 | |
| Injection date reminder | 0.733** | 0.465 | 1.000 | |
| Electronic log | 0.655** | 0.417 | 0.892 | |
| Large grip size | −0.731** | −1.136 | −0.325 | |
| Out-of-pocket cost | £0 | 4.855** | 3.849 | 5.862 |
| £15 | 4.035** | 3.198 | 4.871 | |
| £30 | 3.214** | 2.548 | 3.881 | |
| £50 | 2.120** | 1.680 | 2.560 | |
| £90 | −0.068** | −0.083 | −0.054 | |
| £125 | −1.983** | −2.394 | −1.572 | |
| £150 | −3.351** | −4.046 | −2.656 | |
| £250 | −8.822** | −10.651 | −6.993 | |
| Constant for standard disposable self-injection device | 1.681** | 0.624 | 2.739 | |
| PsA Subgroup | ||||
| Skin sensor | 0.773** | 0.451 | 1.096 | |
| Control of the speed of injection | 0.442** | 0.216 | 0.668 | |
| Step-by-step, on-screen instructions in real time | 0.402** | 0.169 | 0.635 | |
| Injection date reminder | 0.444** | 0.206 | 0.681 | |
| Electronic log | 0.476** | 0.257 | 0.694 | |
| Large grip size | 0.516** | 0.128 | 0.904 | |
| Out-of-pocket cost | £0 | 4.892** | 3.617 | 6.166 |
| £15 | 4.065** | 3.006 | 5.124 | |
| £30 | 3.238** | 2.395 | 4.082 | |
| £50 | 2.136** | 1.579 | 2.692 | |
| £90 | −0.069** | −0.087 | −0.051 | |
| £125 | −1.998** | −2.518 | −1.477 | |
| £150 | −3.376** | −4.255 | −2.496 | |
| £250 | −8.888** | −11.203 | −6.572 | |
| Constant for standard disposable self-injection device | 0.457 | −0.564 | 1.478 | |
| RA Subgroup | ||||
| Skin sensor | 0.589** | 0.303 | 0.875 | |
| Control of the speed of injection | 0.577** | 0.342 | 0.812 | |
| Step-by-step, on-screen instructions in real time | 0.280** | 0.069 | 0.491 | |
| Injection date reminder | 0.480** | 0.237 | 0.723 | |
| Electronic log | 0.433** | 0.204 | 0.662 | |
| Large grip size | 0.193 | −0.235 | 0.622 | |
| Out-of-pocket cost | £0 | 3.708** | 2.905 | 4.512 |
| £15 | 3.082** | 2.414 | 3.750 | |
| £30 | 2.455** | 1.923 | 2.987 | |
| £50 | 1.619** | 1.268 | 1.970 | |
| £90 | −0.052** | −0.064 | −0.041 | |
| £125 | −1.515** | −1.843 | −1.186 | |
| £150 | −2.559** | −3.114 | −2.005 | |
| £250 | −6.738** | −8.198 | −5.277 | |
| Constant for standard disposable self-injection device | −0.933 | −2.757 | 0.891 | |
Notes: All variables, with the exception of out-of-pocket cost, were dichotomous and effects-coded. Cost was included in the model as the interaction of continuous cost and the natural log of income. The preference weights in the table above have been created using the estimated coefficient for cost. Dummy-coded variables for PsA and RA were interacted with the main variables to model the subgroups. The parameters were modeled with normally distributed random parameters, assumed to be the same across the axSpA, PsA, and RA subgroups. Additionally, we included an error component to better accommodate the opt-out bias that could be caused by the standard device alternative. **P≤0.01; * P≤0.05.
Abbreviations: axSpA, axial spondyloarthritis; PsA, psoriatic arthritis; RA, rheumatoid arthritis.